Systems and Methods for Warm Air Pre-Cooling

ABSTRACT

Several methods and systems for pre-cooling warm air in a cooling system are disclosed. The warm air may be return air, fresh air or a combination of return and fresh air. Condensate from a primary cooling element is applied to the wet side of an air-to-air heat exchanger while the warm air passes through the dry side of the heat exchanger. The warm air is pre-cooled by the transfer of heat from the warm air to the condensate, reducing overall energy consumption in the cooling system.

FIELD

The described embodiments relate to systems and methods for cooling relatively warm air, which may be fresh air or return air, or a combination of fresh and return air, in a cooling system. In particular, the described embodiments relate to pre-cooling the warm air to increase efficiency of the cooling system.

BACKGROUND

Cooling systems such as refrigerators, freezers, and air conditioners operate under the laws of thermodynamics and employ refrigeration cycles to cool an object, gas flow, liquid flow, or an area. One example of a refrigeration cycle is the vapor-compression cycle. The vapor-compression cycle is a four step cycle in which a refrigerant is circulated through at least a compressor, condenser, expansion device, and an evaporator.

One example of a refrigeration system is taught by Hancock in U.S. Patent Publication No. 2015/0198340. Hancock discloses a refrigeration system that includes an indoor exchanger, an outdoor exchanger, a fluid collector configured to collect condensate from the indoor exchanger, and a fluid distributor configured to pass the condensate from the fluid collector over at least a portion of the outdoor exchanger. The outdoor exchanger comprises a main coil, and the sub-cooling coil. The indoor exchanger and the outdoor exchanger are operable in at least a cooling mode where the indoor coil is configured to absorb heat in the cooling mode and the outdoor coil is configured to release heat in the cooling mode. The fluid distributor may be configured to pass the condensate over at least a portion of the sub-cooling coil.

A second example of a refrigeration system is taught by Omer in U.S. Patent Publication No. 2013/0061615. Omer discloses a condensate-free cooling unit functionally based on vapor-compression refrigeration cycle. The condensate collected from the evaporator of the cooling unit is routed through a sub-cooling heat exchanger where it exchanges heat with the primary heat exchange medium emerging through the condenser of the cooling unit, thus sub-cooling the primary heat exchange medium to a lower temperature before it enters the expansion valve. Emerging from the sub-cooling heat exchanger, the condensate flows through a condensate outlet pipe into multiple spray nozzles disposed over the condensate outlet pipe. The spray nozzles sprinkle the condensate over the hot air blown into the condenser to reduce its temperature. The cooling unit has a substantially higher coefficient of performance compared to the conventional cooling units utilizing vapor-compression refrigeration cycle, and eliminates the problems of condensate removal persistent in the art.

Existing systems effectively waste the cooling capacity of condensate. There is a need for cooling systems that make use of the cooling capacity of condensate, thereby providing more efficient cooling system.

SUMMARY

This summary is intended to introduce the reader to various aspects of the applicant's teaching, but not to define any specific embodiments. In general, disclosed herein are one or more cooling systems having a pre-cooling heat exchanger positioned in the supply air channel ahead of the cooling system's evaporator and methods for pre-cooling supply air.

In a first aspect, some embodiments of the invention provide a method for pre-cooling a warm airflow in a cooling system, the method including the steps of: (a) providing an air-to-air heat exchanger, wherein the heat exchanger has a wet side and a dry side; (b) collecting a condensate produced within the cooling system; and (c) applying the condensate to the wet side of the heat exchanger, thereby drawing heat from the warm airflow flowing in the dry side of the heat exchanger.

In some examples, the wet side of the heat exchanger includes one or more wet side channels. Applying the condensate to the wet side includes applying a condensate airflow to propel the condensate through the wet side channels.

In some examples, the condensate airflow also blows evaporated condensate out of the wet side.

In some examples, the wet side of the heat exchanger includes one or more wet side channels. The wet side channels have interior surfaces, and applying the condensate to the wet side includes applying at least some of the condensate to at least a portion of the interior surfaces.

In some examples, at least a portion of at least one of the interior surfaces is coated with a hydrophilic coating to promote the spread of condensate on the coated interior surfaces.

In some examples, the wet side of the heat exchanger includes one or more wet side channels. Applying the condensate to the wet side includes spraying the condensate into the wet side channels.

According to some aspects, a system for pre-cooling a warm airflow includes: (a) a cooling system that has a primary cooling element, wherein, in operation, the primary cooling element generates a condensate; (b) a heat exchanger positioned upstream from the primary cooling element in the warm airflow, wherein the heat exchanger has a wet side and a dry side, and wherein, in operation, warm air passes through the dry side; and (c) a condensate application module for applying the condensate to the wet side of the heat exchanger. In operation, the warm airflow is pre-cooled by a transfer of heat from the warm airflow to the condensate in the wet side of the heat exchanger, thereby vaporizing the condensate.

In some examples, the primary cooling element is an evaporator.

In some examples, the condensate application module includes a pump that is fluidically coupled to a condensate reservoir in which the condensate collects. In operation, the pump applies the condensate to the wet side of the heat exchanger.

In some examples, a condensate fan generates a condensate airflow to propel the condensate through the wet side of the heat exchanger.

In some examples, a condensate airflow is generated by diverting a portion of the warm airflow through the wet side of the heat exchanger as a condensate airflow. The condensate airflow propels the vaporized condensate through the wet side of the heat exchanger.

In some examples, after passing through the heat exchanger, pre-cooled warm air is further cooled by passing it through the primary cooling element to form supply air. A condensate airflow is generated by diverting a portion of the supply air through the wet side of the heat exchanger as a condensate airflow. The condensate airflow propels the condensate through the wet side of the heat exchanger.

In some examples, the condensate application module utilizes gravity to transport condensate to the wet side of the heat exchanger.

In some examples, the wet side of the heat exchanger includes one or more wet side channels.

In some examples, a hydrophilic coating applied to at least a portion of at least one of the wet side channels.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will now be described in detail with reference to the drawings, in which:

FIG. 1 is schematic diagram of a cooling system having a pre-cooling heat exchanger positioned in the supply air channel ahead of the cooling system's evaporator;

FIG. 2 is a perspective view of a pre-cooling heat exchanger;

FIG. 3 is a perspective cross sectional view of the pre-cooling heat exchanger of FIG. 2 taken along line 3-3 with flow lines representing condensate, warm airflow, and airflow paths;

FIG. 4 is a perspective cross sectional view of an alternative example of a pre-cooling heat exchanger;

FIG. 5 is perspective view of an alternative example of a pre-cooling heat exchanger;

FIG. 6 is a schematic diagram of an alternative example of a pre-cooling heat exchanger wet side airflow and condensate path;

FIG. 7 is a flowchart illustrating a method for pre-cooling a warm airflow to a cooling system.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Various apparatuses, and/or methods will be described below to provide exemplary embodiments. No embodiment described below limits any claims and any claims may cover apparatuses or methods that differ from those described below. The claims are not limited to apparatuses or methods having all of the features of any one apparatus or method described below or to features common to multiple or all of the apparatuses described below. It is possible that an apparatus or method described below is not an embodiment of any claims. Any apparatus or method described below that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim or dedicate to the public any such apparatus of method by its disclosure in this document.

Referring to FIG. 1, shown therein is a schematic diagram of a first example of a warm air cooling system 100. The system 100 includes a heat exchanger 102, compressor 104, a condenser 106, an expansion valve 108, and an evaporator 110. In the example shown, each of the compressor 104, condenser 106, expansion valve 108, and evaporator 110 are connected in series by a refrigerant line 112 a, 112 b, 112 c, 112 d (collectively referred to as 112), respectively.

A refrigerant is circulated through the refrigerant line 112. For example, the refrigerant enters the compressor 104 as a low-pressure low temperature gas. In the compressor 104, the refrigerant is compressed into a high-pressure high temperature gas. From the compressor 104, the refrigerant flows to a condenser 106. In the condenser 106, the refrigerant is condensed into a liquid. The process of condensing the refrigerant from a gas to a liquid generates heat.

In some examples, the heat generated by the condensing process is removed at the condenser 106 by convection. For example, an airflow may pass over the condenser 106 to remove the heat from the condenser 106. In other examples, the condenser 106 may disperse heat by convention to a liquid flow, or by conduction.

After the refrigerant is compressed, the refrigerant flows through an expansion valve 108. The expansion valve 108 lowers the pressure and temperature of the refrigerant while maintaining the refrigerant's liquid state. Next, the refrigerant passes through the evaporator 110. In the evaporator 110, the refrigerant absorbs heat from its surroundings, which provides a cooling effect to that area.

In some examples, the cooling system 100 described above is commonly known as an air conditioning unit used to provide cool air to a building through the HVAC system. In other examples, the cooling system 100 described above is commonly known as A refrigerator/freezer.

The cooling system 100 operates to cool a volume of return air, typically in a building. A fan 119 draws warm air 114 from the building in ducting 115, and then blows supply air 120 back into the building through ducting 117. Warm airflow 114 is drawn through the heat exchanger 102 in ducting 115 producing a precooled airflow 118, which then passes through the evaporator 110, where it is further cooled and then returned to the building as a cooled supply airflow 120. Heat exchanger 102 is positioned upstream from the evaporator 110 such that warm airflow 114 passes the heat exchanger before reaching the evaporator.

In some embodiments, a cooling system may have a primary cooling element other than an evaporator. For example, the primary cooling element may be a Peltier element or module that generates condensate when used to cool return air. In other embodiments, the primary cooling element may be a heat exchanger using chilled water/brine cooled by vapor absorption chiller or vapor compression chiller. In other embodiments, the primary cooling element may be any element that provides a condensate 116.

As the pre-cooled airflow 118 is cooled within the evaporator 110, condensate may form within the evaporator 110. Condensate forms when at least a portion of the pre-cooled airflow 118 is cooled to a temperature below its dew point temperature and condenses. Accordingly, the condensate formed in the evaporator 110 has a relatively low temperature as compared to the pre-cooled airflow 118 and the warm airflow 114.

System 100 utilizes the cold condensate formed in the evaporator 110 to pre-cool the warm airflow 114 to produce pre-cooled airflow 118.

Still referring to FIG. 1, the condensate formed in the evaporator 110 is pumped through the heat exchanger 102, which is fluidically connected and positioned in the warm air duct 115 ahead of the evaporator 110. The heat exchanger 102 uses the condensate to pre-cool the warm airflow 114. For example, the warm airflow 114 may enter the heat exchanger 102 at a warm air temperature corresponding to the temperature in the building. As the warm airflow 114 passes through the heat exchanger 102, heat from warm airflow 114 transfers to the relatively low temperature condensate. As a result, the pre-cooled airflow 118 that enters the evaporator 110 has a lower temperature than that of the warm airflow 114.

Lowering the temperature of the pre-cooled airflow 118 using the heat exchanger 102 may increase the efficiency of the cooling system 100. For example, it may be desired to produce a cooled supply airflow 120 having a temperature of 20° C. from a warm airflow 114 having a temperature of 30° C. If the heat exchanger 102 lowers the warm airflow 114 temperature by 4° C., the evaporator 110 must only to reduce the pre-cooled airflow 118 by 6° C. to reach the desired cooled supply airflow 120 temperature of 20° C. Without the heat exchanger 102, in the same example, the evaporator 110 would be required to reduce the temperature of the pre-cooled airflow 118 by 10° C. as opposed to 6° C. To achieve this increased cooling, a greater volume of refrigerant may be required to pass through the evaporator, thereby requiring a larger evaporator, which may decrease efficiency of the system and increase operating costs. Alternatively, the refrigerant may be required to enter the evaporator at a relatively lower temperature. In any case, the efficiency of the cooling system would be reduced.

As shown in FIG. 1, the condensate formed in the evaporator may collect in a condensate reservoir 124 prior to use in the heat exchanger 102. In the example shown, the reservoir 124 is connected to the evaporator 110 and the heat exchanger 102 by condensate lines 126 a, 126 b. In this embodiment, a pump 122 pumps the condensate through the condensate line 126 b from the reservoir 124 to the heat exchanger 102. In this embodiment, the pump 122 and condensate line 126 b form a condensate application module that transports and applies the condensate to the wet side of the heat exchanger. In other embodiments, other condensate application modules may be provided. For example, the condensate application module may comprise a condensate line 126 through which condensate is moved from the reservoir 126 to the wet side of the heat exchanger by gravity or other means. In other embodiments, a reservoir may not be provided, and the condensate application module may transfer the condensate from the evaporator to the wet side of the heat exchanger 102.

To collect the condensate, the evaporator 110 may be shaped or oriented to promote movement of the condensate towards an opening in the evaporator 110 connected to the condensate line 126. In some examples, the opening may be at a lower end of the evaporator 110, and the condensate may be urged from the evaporator 110 by a gravitational force. In other examples of the evaporator 110, a pump urges the condensate from the evaporator 110 into the condensate line 126.

In some embodiments of the cooling system 100, the condensate may combine with a water supply, for example water from a tap or from a storage container, prior to use in the heat exchanger 102. The condensate is combined with a water supply when the evaporator 110 does not generate the required amount of condensate to achieve the desired heat transfer in the heat exchanger 102. In other examples, the condensate may be combined with a water supply generated by at least one of mechanical refrigeration chillers, vapor absorption chillers, DX compression systems, heat pumps, magnetic compressors, thermo-electric, sonic, and ultra-sonic cooling devices, ground source heat pumps, geo thermal energy, lake water, sea water, ice slurry, and ice.

Referring now to FIG. 2, shown therein is a perspective view of an example of a heat exchanger 102. In this example, heat exchanger 102 is an air-to-air crossflow heat exchanger, which has a wet side 130 and a dry side 132. The warm airflow 114 flows through one or more dry flow channels 134 of the dry side 132. The warm airflow 114 may be pushed or pulled through the flow channel 134 by a condensate fan 119 (FIG. 1). The condensate flows through one or more wet flow channels 136 of the wet side 130. Optionally the condensate may be pumped into the wet flow channels as described above. In other embodiments, the condensate may be sprayed or pumped at a pressure sufficient to form a liquid suspension in air or an aerosol in the wet side channels 136.

Although the heat exchanger 102 is shown in FIG. 2 to include two wet side 130 flow channels 136 and one dry side 132 flow channel 134, any number of dry side 132 and wet side 130 flow channels 134, 136 may be provided. For example, FIG. 5 illustrates a heat exchanger 502 having multiple wet side flow channel 536 and multiple dry side flow channels 534. Also, although the flow channels 134, 136 are shown in FIG. 2 to be perpendicular to one another, in alternative examples, the flow channels 134, 136 may run counter or parallel to one another or at a non-perpendicular angle.

Referring now to FIG. 3, and as described above, the warm airflow 114 may have a temperature greater than that of the condensate 116 when entering the heat exchanger 102. Therefore, as the warm airflow 114 passes through flow channel 134, heat from the warm airflow 114 transfers by at least one of conduction and convection to the condensate 116 flowing through the wet side 130. As a result of this heat transfer, the temperature of the pre-cooled airflow 118 will be lower than that of the warm airflow 114.

As shown in FIG. 3, the condensate 116 may be sprayed into the wet side flow channels 136 by a pump through nozzles 138. In some embodiments, the condensate 116 is continuously sprayed into the wet side 130 flow channels 136 and in other examples the condensate 116 is periodically sprayed into the wet side 130 flow channels 136. In some embodiments, the condensate 116 sprayed into the flow channels 136 may fully or partially coat an interior surface 142 of the wet flow channels 136. In some embodiments, a hydrophilic coating is applied to the interior surface 142 to promote the formation of a film of the condensate 116 on the interior surface 142. Forming a film of condensate 116 on the interior surface 142 may improve the heat transfer performance of the heat exchanger 102, thereby more effectively pre-cooling warm airflow 114.

As the condensate 116 absorbs heat from the warm airflow 114, the condensate 116 may evaporate within the flow channel 136. The condensate 116 may thereby provide sensible and latent heat consumption, which may improve the effectiveness of the heat exchanger 102. Referring also to FIG. 1, a condensate airflow 140 may pass through the flow channels 136 of the wet side 130 to urge the condensate 116, in a liquid or gas state, through the wet side flow channels 136. The condensate airflow 140 may be pushed or pulled through the flow channels 136, for example by a condensate fan 121, as shown in FIG. 1. In other embodiments, condensate airflow 140 may be drawn from the warm airflow 114, or from the supply airflow 120. In such embodiments, air pressure generated by the system fan 119 may be sufficient to propel the condensate 116 through the wet flow channels 136.

Applying condensate 116 to the heat exchanger 102 to absorb heat from the warm airflow 114 and exhausting the evaporated condensate 116 from the heat exchanger 102 provides a cooling effect to the warm airflow 114.

In other examples, the condensate 116 may not be sprayed into the flow channels 136 through nozzles 138, and rather, the condensate 116 may be dripped or otherwise applied to or deposited into the flow channels 136. In another example of the heat exchanger 102, the condensate 116 flows through the wet side 130 flow channels 136, for example, as a stream. In yet another example, the condensate 116 may flow onto a mesh or other surface located proximate to the condensate airflow 140 entrance to the heat exchanger 102. In this example, the airflow 140 is cooled as it passes through the mesh and the cooled condensate airflow 140 absorbs heat from the warm airflow 114 as they pass through the heat exchanger 102.

Referring now to FIG. 4, shown therein is another example of a heat exchanger 102. In the example shown, the condensate 116 and the airflow 140 enter the wet side 130 flow channels 136 at opposite ends, creating a cross flow. In another example, see FIG. 6, the flow channels 136 may not extend linearly from one side of the heat exchanger 102 to the other, as shown in FIGS. 3 and 4, but may extend in a circuitous manner, effectively creating a longer wet flow channel 136 through the heat exchanger 102.

In FIG. 6, the condensate 116 is shown to be sprayed into the flow channels 136 by nozzles 138. A first portion of the airflow 140 passing through the flow channel 136 flows against or counter to the spray direction of the condensate 116; a second portion of the airflow 140 passing through the flow channel 136 flows generally perpendicular to the spray direction of the condensate; and a third portion of the airflow 140 passing through the flow channel 136 flows with the spray direction of the condensate 116. In other examples, the condensate 116 may be sprayed only in the counterflow direction, only in the flow direction, or only in both the counterflow and flow direction of the airflow 140. In other examples, the condensate 116 is sprayed only from the top or bottom of the heat exchanger 102, irrespective of the flow direction. In yet another example, nozzles 138 may be placed within the flow channels 136.

In FIGS. 4 and 6, the condensate 116 is shown as being sprayed into the flow channels 136 by nozzles 138. In other examples, the condensate 116 may be dripped or otherwise applied or deposited into the flow channels 136.

Although the flow paths of airflow 140 and the warm airflow 114 have been described above as being linear, i.e., ambient air forms the warm airflow 114 which passes through the heat exchanger 102 and then the through evaporator 104, in other examples, the flow paths may have any shape that allows for a heat exchange between the wet flow channels and the warm airflow. For example, in an alternative example of the cooling unit 100 having a heat exchanger 102, a portion of the cooled supply airflow 120 may form at least a portion the airflow 140. In another example, a portion of the pre-cooled airflow 118 forms at least a portion of the airflow 140.

In another example of the cooling unit 100 having a heat exchanger 102, at least a portion of the cooled supply airflow 120 circulates back to the heat exchanger 102 and forms at least a portion of the warm airflow 114. In yet another example, the entire cooled supply airflow 120 circulates back to the heat exchanger 102 multiple times prior to being used to cool a space or an object. Circulating the cooled supply airflow 120 back through the heat exchanger 102 and through the evaporator 110 one or multiple times may reduce the concentration of water in the circulating airflow, i.e., dehumidifying the air.

Reference is now made to FIG. 7, in which a method 700 for pre-cooling a warm airflow to a cooling system is shown. Method 700 begins at step 702, in which a condensate is provided. For example, the cooling system may be an HVAC, cooling or cooling system that produces a condensate may be used to cool a volume of return air, providing a condensate.

Method 700 then proceeds to step 704 in which the condensate is applied to the wet side of an air-to-air heat exchanger. As described above, the condensate is applied in a liquid form. The condensate may be pumped, sprayed, dripped, deposited or other applied to the wet side of the heat exchanger. Optionally, the condensate may be applied to the interior surface of the wet side channels of the heat exchanger. The condensate may be propelled or blown through the wet side channels by a wet side airflow as described above in relation to various examples of counter flow, cross flow or compound flow heat exchangers. Optionally, the interior surface of the wet side channels may have a hydrophilic coating to promote the spread of the condensate on the interior surface.

Method 700 then proceeds to step 706 in which the cooling system is operated to generate a warm airflow that passes through the dry side channels of the heat exchanger. As the warm airflow passes through the dry side channels, it is cooled by the transfer of heat from the warm airflow to the condensate in the wet side channels, through the walls of the heat exchanger. In general, the greater the temperature difference between condensate in the wet flow channels and the return/fresh warm air flow, the greater the pre-cooling effect on the warm air flow will be. The cooled warm airflow may subsequently be further cooled in the cooling system. In practice, the warm airflow may already be flowing through the heat exchanger prior to the application of condensate to the wet side of heat exchanger in step 704. For example, the condensate may be generated only after the cooling system has been operating for some time, and only then will the condensate be available to be applied to the heat exchanger.

The present invention has been described here by way of example only. Various modification and variations may be made to these exemplary embodiments without departing from the spirit and scope of the invention, which is limited only by the appended claims. 

We claim:
 1. A method for pre-cooling a warm airflow in a cooling system, the method comprising: providing an air-to-air heat exchanger, wherein the heat exchanger has a wet side and a dry side; collecting a condensate produced within the cooling system; and applying the condensate to the wet side of the heat exchanger, thereby drawing heat from the warm airflow flowing in the dry side of the heat exchanger.
 2. The method of claim 1 wherein the wet side of the heat exchanger includes one or more wet side channels, and wherein applying the condensate to the wet side includes applying a condensate airflow to propel the condensate through the wet side channels.
 3. The method of claim 2 wherein the condensate airflow also blows evaporated condensate out of the wet side.
 4. The method of claim 1 wherein the wet side of the heat exchanger includes one or more wet side channels, wherein the wet side channels have interior surfaces, and wherein applying the condensate to the wet side includes applying at least some of the condensate to at least a portion of the interior surfaces.
 5. The method of claim 4 wherein at least a portion of at least one of the interior surfaces is coated with a hydrophilic coating to promote the spread of condensate on the coated interior surfaces.
 6. The method of claim 1 wherein the wet side of the heat exchanger includes one or more wet side channels, and wherein applying the condensate to the wet side includes spraying the condensate into the wet side channels.
 7. A system for pre-cooling a warm airflow, the system comprising: a cooling system that has a primary cooling element, wherein, in operation, the primary cooling element generates a condensate; a heat exchanger positioned upstream from the primary cooling element in the warm airflow, wherein the heat exchanger has a wet side and a dry side, and wherein, in operation, warm air passes through the dry side; and a condensate application module for applying the condensate to the wet side of the heat exchanger, wherein, in operation, the warm airflow is pre-cooled by a transfer of heat from the warm airflow to the condensate in the wet side of the heat exchanger, thereby vaporizing the condensate.
 8. The system of claim 7 wherein the primary cooling element is an evaporator.
 9. The system of claim 7 wherein the condensate application module includes a pump that is fluidically coupled to a condensate reservoir in which the condensate collects, and wherein, in operation, the pump applies the condensate to the wet side of the heat exchanger.
 10. The system of claim 7 further comprising a condensate fan to generate a condensate airflow to propel the condensate through the wet side of the heat exchanger.
 11. The system of claim 7 further wherein a condensate airflow is generated by diverting a portion of the warm airflow through the wet side of the heat exchanger as a condensate airflow, wherein the condensate airflow propels the vaporized condensate through the wet side of the heat exchanger.
 12. The system of claim 7 further wherein, after passing through the heat exchanger, pre-cooled warm air is further cooled by passing it through the primary cooling element to form supply air, and wherein a condensate airflow is generated by diverting a portion of the supply air through the wet side of the heat exchanger as a condensate airflow, wherein the condensate airflow propels the condensate through the wet side of the heat exchanger.
 13. The system of claim 7 wherein the condensate application module utilizes gravity to transport condensate to the wet side of the heat exchanger.
 14. The system of claim 7 wherein the wet side of the heat exchanger includes one or more wet side channels.
 15. The system of claim 7 further comprising a hydrophilic coating applied to at least a portion of at least one of the wet side channels. 